Let's walk through the design of the top-down Azteca sweater, a round-yoked scoop-neck sweater knitted of bits of different colors of Amazon cotton in the Syncopated Tweed pattern.
Here's the actual pattern I used to knit the sweater:
It really doesn't have to be any more complicated than that. I ordinarily put this stuff on the computer, but mine was broken when I designed this sweater, so I did the work longhand.
The first thing I wrote, on the upper right hand corner of the page, is the gauge of Syncopated Tweed on the size 4 needles I'm using: 5.12 stitches and 8 rows per inch.
I ordinarily make a little sketch of the sweater with all of the dimensions I'll be using written in. Sometimes (as in this case), I simply use a pre-made standard size sketch as a reference. Many knitting reference books contain standard size sketches for both raglans and set-in sleeve designs. For a round-yoke sweater, I use raglan dimensions.
You can also find standard sizing information online.
At the top center of the page, there's a little sketch of the back of the neck and the shoulders. The back neck of this sweater is 5" and each shoulder is 1.5". I therefore need to cast on 8" or 40 stitches.
My raglan line (the length between the neck and underarm) was 9 inches or 72 rows. I thus have 72 rows across which to space the yoke increases. In a round yoke sweater, the increases are bunched in a few groups rather than every other row as in a raglan. In this particular stitch pattern, the increases need to happen on plain rows. I decided to work my increases in 6 groups, every 12 rows, starting with row 9 of the pattern.
How many stitches do I need? I'll need 184 stitches for the body at the underarm plus 72 stitches for each arm. I'll need to subtract the underarm cast-ons from the sleeves and the body. (Here I notice a mistake; I only subtracted one underarm cast-on, or 6 stitches, from the body, instead of both underarm cast-ons or 12 stitches. This makes the sweater an inch wider at the body. Oh well. It worked anyway.)
I charted my neck increases on knitter's graph paper to get a nice smooth curve, so I'll just note here that I have 30 stitches total for the neck increases.
I've chosen 6 stitches for the underarm cast-on. I usually cast on between one and two inches of stitches at the underarm, fewer for small children and more for deep-chested people. The underarm cast-on should be about half of the underarm depth; more and the cast-on line shows around the edges of the arm, less and the wearer has restricted movement at the underarm.
Let me pretend I needed 192 stitches for the body so I can do the math right.
(192 stitches for the body - 12 stitches for underarm cast ons) + (72 stitches for each arm - 6 underarm cast ons) * 2 for two arms = 310 stitches
310 stitches - (40 stitches we cast on + 30 stitches for neck increases) = 240 stitches to be increased
240 stitches to be increased / 6 increase rows = 40 stitches to be increased per increase row
I then note that those increases are to happen on row 9 of my 12-row pattern. Since the neck shaping complicated matters a bit, I decided to count stitches right before each increase row and figure out the increase pattern for Azteca.
In general, for a round-yoke sweater, this is my formula for figuring out the increase pattern:
(number of stitches present / number of stitches to increase) = magic number
The magic number is usually something messy like 1.34. I take the decimal part of that number and find a pretty close fraction, in this case 1/3. 1/3 of the time, we'll add an extra stitch before increasing and the other 2/3 of the time, we'll knit the whole part of the magic number of stitches before increasing. In this case, our increase row would be:
* (k1, make 1) 2x, (k2, make 1) *
When you don't have neck increases changing your numbers on you, the increase rows keep the same pattern, simply increasing the number of stitches you knit before increasing. So subsequent increase rows would be:
* (k2, make 1) 2x, (k3, make 1) *
* (k3, make 1) 2x, (k4, make 1) *
* (k4, make 1) 2x, (k5, make 1) *
* (k5, make 1) 2x, (k6, make 1) *
* (k6, make 1) 2x, (k7, make 1) *
There's no rule that says all of the increase rows need to be the same. If the numbers come out ugly, you can move things around to make your life easier. You can do more or fewer increases in some increase rows if that works better. The knitting police won't come after you, I promise.
I've decided not to use short row bust darts in this sweater because of the slip-stitch color pattern with the long slip stitches. I am doing waist shaping, decreasing 30 stitches over 6". I'll be doing those decreases on row 1 of my stitch pattern, which is always purple.
I don't yet know what I'm going to do after the waist, nor what I'm going to do with the arms. I'm not sure how much yarn I have, exactly, and I want to see how the stitch pattern behaves towards the edges. One of the nice parts of top-down design is that we can delay these decisions until later in the process, when we have a better idea how the sweater will turn out and how much yarn we have.